System and method for geothermal heat harvesting

ABSTRACT

A system and method for deploying a heat harvesting system and for harvesting heat from a geothermal well using one or more heat pipes. A heat exchanger may receive heat from one or more heat pipes for transfer to a heat receiving component. The heat pipes may be thermally coupled to the heat exchanger via a thermal gap material having a relatively low thermal conductivity. A mounting component may engage heat pipes and define a thermal gap between the heat pipes and heat exchanger. A heat spreader, having a relatively high thermal conductivity, may be used to transfer heat from the heat pipes to the thermal gap material and help define a working temperature for the heat pipes. A heat pipe deployment system may include anti-buckling supports and/or a guide to help keep the heat pipes from buckling and to guide the heat pipes into corresponding well bores during deployment.

BACKGROUND

Harvesting of heat energy from a geothermal well (i.e., an undergroundregion) can be useful for various purposes, including electrical energygeneration, transferring heat to above ground systems for use in spaceheating, industrial or other processes, or other uses.

SUMMARY OF INVENTION

Aspects of the invention provide for heat harvesting from a geothermalwell (i.e., an underground region) using one or more heat pipes. In someembodiments, one or more heat pipes may be arranged in a tree-type orother configuration and used to transfer heat from portions of thegeothermal well to a heat exchanger and a heat receiving component, suchas a heat exchange liquid, a thermoelectric device, or other componentthat receives heat, e.g., for use in generating electricity.

In one aspect of the invention, a geothermal heat harvesting systemincludes a heat exchanger arranged to receive heat from a geothermalwell for transfer to a heat receiving component. The heat exchanger mayinclude a cylindrical body or pipe that receives heat at its outer walland transfers that heat to a working fluid, such as water or steam, inthe heat exchanger. The heated fluid may be conducted out of the heatexchanger to a heat receiving component such as a thermal storagedevice, a thermal storage medium, and/or one or more thermoelectric orother power conversion devices, such as a steam turbine and generator.

One or more heat pipes may be arranged in the well to transfer heat fromthe well to the heat exchanger, e.g., heat pipes may be arranged aroundthe heat exchanger and extend outwardly from the heat exchanger into hotrock or other medium of the geothermal well. The heat pipes may bearranged in one or more levels, e.g., a plurality of heat pipes may bearranged around the heat exchanger and extend radially into thegeothermal well (e.g., 20 to 100 feet) at one or more vertical positionsin the well. The one or more heat pipes may each have an evaporatorsection positioned within the geothermal well and distant from the heatexchanger, and a condenser section positioned adjacent the heatexchanger. Thus, heat received at the evaporator section may betransferred to the condenser section, which relays the heat to the heatexchanger. The heat pipes may be arranged in any suitable way, and mayinclude a thermosiphon, a loop thermosiphon, a pulsating heat pipe,and/or an osmotic heat pipe. The heat pipes may have a length of 40 to120 feet (or other suitable length such as up to 300 feet), and may havethe condenser section aligned along a length of the heat exchanger. Forexample, the condenser section of the heat pipes may be uniformly spacedfrom the heat exchanger along a length of the condenser section of 2 to20 feet. Thus, portions of the condenser section may be spaced from theheat exchanger to achieve a defined thermal gap or thermal resistancewhich helps to control the heat transfer rate between the heat pipes andthe heat exchanger, allowing the heat pipe to operate at an optimal orother designed working temperature.

In some embodiments, a thermal gap material may be positioned in athermal gap between the condenser section of the one or more heat pipesand the heat exchanger. The thermal gap material may provide a thermalcoupling between the one or more heat pipes and the heat exchanger suchthat a desired temperature drop is incurred when heat is transferredbetween the one or more heat pipes and the heat exchanger via thethermal gap material. The thermal gap material may have a relatively lowthermal conductivity, e.g., less than about 12 W/m-K or around 0.6W/m-K, so as to meter heat transferred to the heat exchanger incomparison to a condition in which the heat pipe(s) are coupled to theheat exchanger by a steel or other relatively highly thermallyconductive metal connection. A conduction length of the thermal gap andthe thermal conductivity of the thermal gap material may be arranged todefine a working temperature for the at least one heat pipe, which maybe elevated above the operating temperature of the heat exchanger by 10to 40% of the temperature difference between the heat exchanger and thegeothermal resource and may allow the heat pipe(s) to harvest heat fromthe geothermal resource more efficiently than at lower temperatures. Amajority of heat transferred between the heat pipe(s) and the heatexchanger may be transferred through the thermal gap material, e.g.,60%, 70%, 90%, 95% or more of heat transferred between the two may betransmitted through the thermal gap material.

In some embodiments, a heat spreader may be provided between the atleast one heat pipe and the thermal gap material to help transfer heatfrom the heat pipe to the thermal gap material. Thus, the heat spreadermay have a relatively high thermal conductivity, e.g., above 12 W/m-K,and be in direct thermal contact with the at least one heat pipe andwith the thermal gap material. While the heat spreader may be arrangedin different ways, the heat spreader may generally present a relativelysmaller surface area to the heat pipe(s) for receiving heat and arelatively larger surface area to the thermal gap material. For example,the heat spreader may include a sleeve positioned over the heat pipe,and/or may include a plate with a partial cylindrical shellconfiguration that generally conforms to the outer periphery of a heatexchanger. The heat spreader may therefore effectively increase asurface area of the heat pipes for transferring heat to the thermal gapmaterial.

In some embodiments, the heat pipe(s) may be mechanically coupled by acollar or other mounting component which also helps define the thermalgap between the heat pipe(s) and the heat exchanger. For example, acollar may engage with one or more heat pipes and be configured toreceive the heat exchanger at an inner side of the collar, i.e., thecollar may extend around the heat exchanger. The collar may help toposition the one or more heat pipes from the heat exchanger so as todefine a thermal gap, e.g., one or more spacer elements such asprotrusions extending radially inwardly from the collar inner side mayhelp maintain a desired distance between the heat pipe(s) and the heatexchanger. Two or more relatively short collars (e.g., 1 to 2 feet long,or more or less) may be employed, and may be spaced from each otheralong the condenser section of one or more heat pipes, e.g., at adistance of 10 to 20 feet or more (or less), so that portions of theheat pipes extending between the collars are suitably positioned fromthe heat exchanger to define a thermal gap. Alternately, a collar mayhave a relatively long length, e.g., of 10 to 20 feet or more (or less),and be arranged as a solid cylindrical shell, e.g., to control fluidflow in the thermal gap between the heat pipes and the heat exchangeralong the length of the shell. In some embodiments, the collar mayinclude one or more openings in the shell to permit fluid flow, e.g., toallow relatively hot fluid in the geothermal well to flow into the spacebetween the collar and the heat exchanger and allow relatively coolfluid to exit. A collar or other mounting component may, or may notfunction as a heat spreader.

In one aspect of the invention, a heat pipe and mounting componentapparatus for use with a heat exchanger in harvesting geothermal heatincludes one or more heat pipes each having two end portions and anelongated central portion, and a mounting component dimensioned toengage and thermally couple with at least one heat pipe at or near oneof the said end portions. The mounting component may be dimensioned toextend at least partially around a portion of a perimeter of the heatexchanger. For example, the mounting component may include a collar orsleeve arranged to receive a portion of a heat exchanger in the centralopening of the collar, and/or may include a shoe or plate that extendsaround only a part of the heat exchanger. The portion of the mountingcomponent that faces the heat exchanger may be shaped to generallyconform to the shape of an adjacent portion of the heat exchanger, e.g.,so that a generally uniform gap may be present between the mountingcomponent and the heat exchanger. As will be understood by those ofskill in the art, a uniform gap may provide for a uniform conductionlength for heat passing between the mounting component and the heatexchanger, and thus uniform and predictable heat flow.

An interface material, or thermal gap material, may be positionedbetween, and thermally couple, the heat exchanger and the mountingcomponent. The interface material may have a thermal conductivity thatis less than the mounting component, and thus may provide a desiredthermal gap or resistance to heat flow, e.g., to allow the one or moreheat pipes to operate within an optimal working temperature range. Asdiscussed in detail below, having a heat pipe operate in an optimalworking temperature range may allow for more efficient heat harvesting.Thus, the thermal conductivity of the interface material may be selectedto define an optimal heat pipe working temperature for use in harvestinggeothermal energy, e.g., may be 0.5 to 12 W/m-K. Other characteristicsof the thermal coupling of the heat pipe(s) to the heat exchanger, suchas the surface area of the mounting component that faces the heatexchanger and the conduction length of the thermal gap, may be similarlyselected to define, or otherwise be consistent with, an optimal heatpipe working temperature. In some embodiments, the optimal heat pipeworking temperature may be higher than the temperature of the heatexchanger by an amount between 10% and 40% of the temperature differencebetween the heat exchanger and the geothermal resource. In contrast tothe thermal gap material, the mounting component may have a relativelyhigh thermal conductivity that is selected to promote heat spreadingfrom the one or more heat pipes for transfer to the thermal gapmaterial. As a result, a surface area of contact between the thermal gapmaterial and the mounting component, and the thermal conductivity andthickness of the thermal gap material may be the primary controllingfactors in defining a working temperature of the one or more heat pipesthermally coupled to the mounting component.

A surface area of the mounting component that faces the heat exchangermay define the surface area of contact between the thermal gap materialand the mounting component, and so may help define heat flowcharacteristics of the heat pipe/heat exchanger thermal junction. Insome embodiments, the mounting component may have a surface area facingthe heat exchanger (i.e., a surface area that functions to transfer amajority of heat to the heat exchanger) that is larger than a surfacearea presented by the at least one heat pipe to the heat exchanger. Thatis, the mounting component may present a larger surface area for heattransfer to the heat exchanger than the heat pipe(s) would present inthe absence of the mounting component. Such an arrangement may allow forhigher heat flow rates, and/or better control over the heat flow rate ofthe thermal junction. In one embodiment, the surface area of themounting component facing the heat exchanger may be at least 1 to 10times the surface area presented by the at least one heat pipe to theheat exchanger.

The mounting component may also function to help deploy one or more heatpipes in a well and/or perform other functions. For example, themounting component may include an upper collar portion and a lowercollar portion, with the upper collar portion having one or more heatpipes fixed to the upper collar portion and the lower collar portiondefining a heat pipe guide feature to receive at least one heat pipethat is fixed to the upper collar portion. The heat pipe(s) may move ina sliding relationship in the guide feature as the upper collar portionis moved toward the lower collar portion, e.g., to help guide the heatpipe(s) into side holes formed from a main well as the heat pipes arelowered into the main well bore.

In another aspect of the invention, a heat pipe and mounting componentapparatus for use with a heat exchanger in harvesting geothermal heatincludes one or more heat pipes each having two end portions and anelongated central portion, and a mounting component arranged anddimensioned to engage with an end portion of the one or more heat pipesand to position the end portion within a specified distance of aperimeter of the heat exchanger to define a thermal gap between the oneor more heat pipes and the heat exchanger. The thermal gap may be filledby a thermal gap material that thermally couples the one or more heatpipes to the heat exchanger. The thermal gap material may have a thermalconductivity of 0.5 to 12 W/m-K that is less than the heat pipes,mounting component or heat exchanger outer surface, e.g., the thermalgap material may be water (including brine or water containing a varietyof dissolved minerals and other substances) or a thermal grout, such asa cement-like substance with an engineered thermal conductivity. Themounting component may, or may not assist in transferring heat to theheat exchanger, e.g., may play a minor role in actual heat transfer. Forexample, a majority of heat transferred from a heat pipe to the heatexchanger may occur along portions of the heat pipe where no mountingcomponent, heat spreader or other structure is located. In oneembodiment, the mounting component includes an upper collar and a lowercollar which are fixed to a set of heat pipes and are spaced from eachother. Thus, an exposed portion of the heat pipes may extend between thecollars and be spaced from the heat exchanger by a desired thermal gap.A bulk of heat transferred from the heat pipes to the heat exchanger mayoccur along the exposed heat pipe sections extending between thecollars. In some embodiments, a heat spreader in the form of a sleevemay be arranged around the heat pipes, e.g., the heat pipes may includetwo concentric tubes with the outer tube functioning as a heat spreader.

In another aspect of the invention, a heat pipe deployment system mayinclude one or more anti-buckling supports to assist in inserting one ormore heat pipes in a geothermal well. For example, a geothermal well maybe prepared for deployment of heat pipes by drilling or otherwiseforming bores that extend radially outwardly from a main well bore.These bores may each receive at least one corresponding heat pipe, whichis inserted into the bore from the main well bore and may have a lengthof 100 feet or more. To assist in inserting the heat pipe(s) intocorresponding radial bores, one or more anti-buckling supports may beengaged with the heat pipe(s) to help keep the heat pipe(s) relativelystraight when an axial load is applied to the pipe(s) to push thepipe(s) into the bore(s). The anti-buckling supports may disengage fromthe heat pipe(s) under particular conditions, such as when an axialforce on the heat pipe(s) relative to the support exceeds a threshold.Thus, the anti-buckling supports may release from the heat pipes toallow their further insertion into a bore.

The system may additionally, or alternately include a heat pipe guide,or “kicker,” that helps to guide the heat pipe(s) into their respectivebore. For example, the heat pipe guide may be arranged in the main wellbore and include a flared or curved guide channel for one or more heatpipes. The guide channel may engage a heat pipe, e.g., at the distalend, and guide the heat pipe into a radially extending bore. The heatpipe guide may also be used to guide a tool that forms radiallyextending heat pipe bores, such as a rotary drilling tool, high pressurejet device, etc.

Thus, in one aspect of the invention, a heat pipe and mounting componentapparatus for use with a heat exchanger in harvesting geothermal heatmay include one or more heat pipes each having two end portions and anelongated central portion and an upper collar engaged with an endportion of the one or more heat pipes. An anti-buckling support,separate from the upper collar, may be attached to the one or more heatpipes at a location below and away from the upper collar. Theanti-buckling support may be releasably attached to the one or more heatpipes to allow movement of the one or more heat pipes relative to theanti-buckling portion in a direction along a length of the one or moreheat pipes, e.g., in response to an axial force on the heat pipe(s)relative to the anti-buckling support that exceeds a threshold.

In some embodiments, the anti-buckling support is attached to the one ormore heat pipes by a frangible connection, such as a metallurgical jointor adhesive, that fixes the heat pipes relative to the anti-bucklingportion until a force applied to the one or more heat pipes exceeds athreshold value. The frangible connection may fix the anti-bucklingsupport relative to the heat pipes and the upper collar until a forcemoving the upper collar toward the anti-buckling portion exceeds thethreshold value. For example, as a force is applied to the upper collarand/or heat pipes to push the heat pipes downwardly and into respectiveradial bores, the heat pipes and attached anti-buckling support may movedownwardly together. However, at a specified point, such as where theanti-buckling support reaches the radial bores, the anti-bucklingsupport may disengage from the heat pipes. In some embodiments, when theanti-buckling support disengages from the heat pipe(s), theanti-buckling portion may slide along the heat pipes such that the uppercollar and anti-buckling portion move toward each other. In otherembodiments, the anti-buckling portion may completely detach from theheat pipes.

In some embodiments, a lower heat pipe guide portion may also beprovided which includes one or more heat pipe guides arranged to guidethe one or more heat pipes in deployment in the geothermal well indirections away from the heat exchanger. For example, the anti-bucklingportion may be positioned between the upper collar and lower guideportion, and the upper collar may be movable toward the lower guideportion to deploy the one or more heat pipes in the well, e.g., intoradially extending bores from a main well bore. As noted above, two ormore collars may be engaged with the heat pipes at an upper end, e.g., alower collar may be engaged with the one or more heat pipes at alocation below the upper collar and above the anti-buckling support. Insome embodiments, the upper and/or lower collars, the anti-bucklingsupport and/or the lower heat pipe guide may include two or more partsthat are engagable with each other so as to receive a drill string or aportion of the heat exchanger between the two parts. For example, thecomponents may be arranged in a clam shell or other configuration sothat the components can be assembled over and around an existing drillstring at the surface of the well.

In another aspect of the invention, a method for deploying one or moreheat pipes in a geothermal well for use with a heat exchanger inharvesting geothermal heat includes providing one or more heat pipeseach having a first portion engaged with an upper collar and a secondportion engaged with an anti-buckling portion separate from the uppercollar and attached to the one or more heat pipes at a location belowthe upper collar and above a distal end of the one or more heat pipes.The distal end of the one or more heat pipes may be inserted into acorresponding well bore, e.g., a bore that extends radially from a mainwell bore, and a force may be exerted on the one or more heat pipes soas to disengage the one or more heat pipes from the anti-bucklingsupport. For example, the heat pipes may be forced downwardly into themain well bore such that the distal ends of the heat pipes move into aradially extending bore. The anti-buckling support may help keep theheat pipes generally straight in the main well bore (e.g., preventbuckling) until a certain point, such as when the anti-buckling supportreaches a point where the heat pipes exit the main well bore and enter aradially extending bore. At this point, the heat pipes may detach fromthe anti-buckling support, allowing the one or more heat pipes to movein a direction along a length of the one or more heat pipes relative tothe anti-buckling portion. The upper collar may be arranged adjacent aheat exchanger in the geothermal well, e.g., to position a condenserportion of the one or more heat pipes at a desired distance from theheat exchanger and thereby establish a desired thermal gap.

In another aspect of the invention, a geothermal heat harvesting systemincludes a heat exchanger arranged to transfer heat from a geothermalwell to a heat receiving component, one or more heat pipes arranged inthe well to transfer heat from the well to the heat exchanger, the oneor more heat pipes having an evaporator section and a condenser section,a heat spreader in direct thermal contact with the condenser section ofat least one heat pipe, and a thermal gap material positioned in athermal gap between the heat spreader and the heat exchanger. The heatspreader may have a surface area and a first thermal conductivity, andthe thermal gap material may have a second thermal conductivity that isless than the first thermal conductivity. As discussed above, a surfacearea of the heat spreader that functions to transfer a majority of heatto the heat exchanger, along with the thermal conductivity of thethermal gap material and a thickness of the thermal gap material (whichdefines the conduction length for heat moving between the heat spreaderand the heat exchanger) may define a working temperature for the one ormore heat pipes. In one embodiment, the heat spreader is metal and/orhas thermal conductivity over 12 W/m-K, and the thermal gap material hasa thermal conductivity of 0.5 to 12 W/m-K. The heat spreader may have acylindrical shape, a partial cylindrical shell configuration, include asleeve and/or a plate, etc., and may have a surface contour arranged togenerally conform to a surface contour of a heat exchanger portion withwhich the heat spreader is thermally coupled. This arrangement may helpdefine a uniform thermal gap between the heat spreader and the heatexchanger.

The geothermal heat harvesting system may be employed for any suitablepurpose, e.g., the heat receiving component may include a heat exchangefluid, one or more conduits to conduct a heat exchange fluid, a thermalstorage device, a thermal storage medium, and/or one or morethermoelectric or other power conversion devices. Also, heat pipes usedin this or other embodiments may include a thermosiphon, a loopthermosiphon, a pulsating heat pipe, osmotic heat pipe and/or otherpossible specific configurations driven by other forces such aselectro-osmotic, acoustic, electrical, and/or magnetic.

In another aspect of the invention, a method for deploying a thermalcoupling for a geothermal device includes providing a heat exchanger ina geothermal well, providing one or more heat pipes in the geothermalwell, each of the heat pipes including a condenser section locatednearer the heat exchanger than an evaporator section of the heat pipe,providing a heat spreader thermally coupled to the condenser section ofat least one heat pipe, the heat spreader having a first thermalconductivity, and providing a thermal gap material that extends between,and thermally couples, the heat spreader and the heat exchanger, thethermal gap material having a second thermal conductivity that is lessthan the first thermal conductivity. Components of the system, such asthe heat spreader, thermal gap material, etc., may have any of thosefeatures described herein.

In yet another aspect of the invention, a method for designing ageothermal heat harvesting system includes determining an optimalworking temperature range for one or more heat pipes used to transferheat from portions of a geothermal well to a heat exchanger, determininga first surface area of a heat spreader to be thermally coupled to theheat exchanger based on the optimal working temperature range, the heatspreader being designed to provide heat to the heat exchanger via athermal gap material having a thermal conductivity that is less than theheat spreader, and providing the heat spreader having the first surfacearea. The thermal conductivity of the thermal gap material and/or thethickness of the thermal gap material may also be determined based onthe optimal working temperature range. In one embodiment, an optimalworking temperature range may be determined by modeling fluid flow inthe geothermal well in response to heat removal by the one or more heatpipes from portions of the geothermal well.

These and other aspects of the invention will be apparent from thefollowing description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the invention are described with reference to the followingdrawings in which numerals reference like elements, and wherein:

FIG. 1 shows a schematic drawing of a geothermal heat harvesting systemin an illustrative embodiment;

FIG. 2 shows a schematic drawing of a geothermal heat harvesting systemhaving multiple heat pipes arranged at multiple levels in a well;

FIG. 3 shows a partial side view of a thermal transfer arrangement fortransferring heat from one or more heat pipes to a heat exchanger in anillustrative embodiment;

FIG. 4 shows a cross sectional top view of the thermal transferarrangement of FIG. 1 along the line 4-4 in one embodiment;

FIG. 5 shows a cross sectional top view of the thermal transferarrangement of FIG. 1 along the line 4-4 in another embodiment;

FIG. 6 shows an arrangement for deploying thermal gap material in anillustrative embodiment;

FIG. 7 shows an arrangement for deploying thermal gap material in anembodiment in which one or more ports are used to position thermal gapmaterial in a gap;

FIG. 8 shows a perspective view of a heat pipe deployment system priorto heat pipe deployment;

FIG. 9 shows a cross sectional view along the line 9-9 in FIG. 8;

FIG. 10 shows an anti-buckling support in an illustrative embodiment;

FIG. 11 shows a collar having a clam shell arrangement;

FIG. 12 shows a cross sectional view along the line 12-12 in FIG. 8;

FIG. 13 shows a perspective view of a heat pipe deployment system in anillustrative embodiment;

FIG. 14 shows a close up view of a heat pipe guide in the FIG. 13embodiment;

FIG. 15 shows an illustrative embodiment including a multi-part mountingcomponent in an assembled condition;

FIG. 16 shows the FIG. 15 embodiment in a pre-deployment condition;

FIG. 17 shows the mounting component and heat pipes of the FIG. 15embodiment in a deployed condition;

FIG. 18 shows an illustrative embodiment of heat exchanger portionsincluding one or more alignment features;

FIG. 19 shows a top perspective view of an upper portion of a mountingcomponent in an illustrative embodiment;

FIG. 20 shows a cross sectional view of the FIG. 19 embodiment along theline 20-20 in FIG. 15;

FIG. 21 shows a cross sectional side view of the FIG. 19 embodiment;

FIGS. 22-25 show illustrative embodiments for saddles useable forengaging one or more heat pipes; and

FIG. 26 shows a cross sectional side view of an arrangement in whichheat pipes extend into a heat exchanger space.

DETAILED DESCRIPTION

Aspects of the invention are not limited in application to the detailsof construction and the arrangement of components set forth in thefollowing description or illustrated in the drawings. Other embodimentsmay be employed and aspects of the invention may be practiced or becarried out in various ways. Also, aspects of the invention may be usedalone or in any suitable combination with each other. Thus, thephraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting.

FIG. 1 shows a schematic view of a geothermal heat harvesting system 100in an illustrative embodiment. It should be appreciated, however, thatthis is only one example configuration for a heat harvesting system 100and that other system types or configurations are possible for use withaspects of the invention. For example, in this embodiment, a heatreceiver 6 includes a steam generator, turbine, and electricitygenerator coupled to the turbine (along with other suitable components,such as control systems, valves, heat and/or electricity storagesystems, etc.) that use heat harvested from the geothermal well 1 togenerate electricity. Heat may be delivered from the well 1 to the heatreceiver 6 in the form of steam or other heated fluid. However, the heatreceiver 6 may be arranged in other ways. For example, harvested heatmay be used to heat a building, to heat materials used in an industrialprocess (such as oil shale heating to recover petroleum), to generateelectricity via one or more thermoelectric devices, to provide heat fora heat pump system, and so on. Moreover, the heat receiver 6 may includecomponents below ground, such as thermoelectric components (e.g.,Peltier or similar devices) located in the well 1 that generateelectricity, additional heat exchangers, and so on.

It should also be understood that a geothermal well 1, as used herein,may include any underground region from which heat is harvested. In thisembodiment, the well 1 is accessed by drilling using an above-surfacedrilling system, but the well 1 may be accessed in other ways, such asby digging a hole, providing below-ground system 100 components in thehole, and again filling the hole, whether with soil originally dug fromthe hole or other materials. Also, drilling to provide components in awell 1 may be done by rotating bit, fluid jet injection and/or any othersuitable techniques, or combinations of such techniques.

In this embodiment, the geothermal well 1 includes fluid (such asunderground water) that has at least some ability to flow in the well 1(i.e., in a region around the below-ground components of the system100), and therefore move heat in the well 1 by convection. However,embodiments described herein need not exchange fluid in the well 1(e.g., underground water or steam) with fluid used by the heatharvesting system 100 to carry heat to the heat receiver 6. Instead, anyfluid used by the system 100 to transport heat from the well 1 to theheat receiver 6 is generally isolated from rock, underground waterand/or other features of the well. It should also be understood thataspects of the invention are not limited to such applications, however,but may be used in “dry” well 1 conditions in which fluid is not veryfree to flow in the well 1, or other well conditions.

The system 100 in FIG. 1 includes a heat exchanger 2 that in thisembodiment transfers heat harvested from the well 1 to fluid that flowsbetween the heat exchanger 2 and the heat receiver 6. The fluid may begas and/or liquid (such as steam and/or water) or any other material,such as a molten salt, glycol solution or other material. In thisembodiment, the heat exchange fluid flows in a closed loop system,although open loop flow may be used in some embodiments. Flow of theheat exchange fluid may be driven by pump, gravity, capillary actionand/or other driving forces. In one embodiment, the heat exchanger mayinclude one or more “hot” pipes positioned at an outer periphery of theheat exchanger 2 that carry heated fluid upwardly, and one or more“cold” pipes positioned at an interior of the heat exchanger 2. Inanother arrangement, the heat exchanger 2 includes a single outer pipe(e.g., used to conduct heated fluid to the receiver 6), and a singleinner pipe (e.g., used to deliver relatively cool fluid to the well 1for heating). The heat exchanger 2 may include other features to enhanceheat transfer, such as serpentine flow tubes or other pathways, finnedtube segments, baffles, and other components to assist in transferringheat to the working fluid, whether by increasing a surface area ofheated components presented to the working fluid, slowing or divertingflow of the working fluid in one or more sections of the heat exchanger,etc. Also, the heat exchanger 2 may be arranged to transfer heat to theworking fluid over an extended length of the well 1, may be arranged totransfer heat at multiple, distinct sections or levels of the well(e.g., which are vertically displaced), or may transfer heat to theworking fluid only in one well section (e.g., near a bottom of the well1). However, other arrangements are possible.

In accordance with an aspect of the invention, one or more heat pipes 5are coupled with a mounting component 3 (in this example a collar orother support arranged to mount one or more heat pipes) that ispositioned around at least part of an outer periphery of the heatexchanger 2 and that positions the heat pipes 5 for transfer of heat tothe heat exchanger 2 via a thermal gap material 4. Thus, in thisexample, heat is harvested by the heat pipes 5 that extend radially fromthe mounting component 3 into portions of the geothermal well 1surrounding a well bore in which the heat exchanger 2 is positioned. Theharvested heat from the heat pipes 5 is transmitted to the thermal gapmaterial 4, e.g., by conduction and/or convection, which in turntransfers heat to the heat exchanger 2. In some embodiments, heat may beconducted from the heat pipes 5 to the mounting component 3 whichtransfers heat to the thermal gap material 4 and into an outer wall orother suitable portion of the heat exchanger 2. Accordingly, a liquid orother fluid flowing in the heat exchanger 2 picks up the heat andtransports it to the heat receiver 6. Although only two heat pipes areshown, any suitable number of such heat pipes assemblies may be arrayedalong the length of the heat exchanger 2 to provide the required heatharvesting rate for a particular geothermal energy system 100. Forexample, FIG. 2 shows an arrangement in which the heat exchanger 2 islocated in a main well bore 11, and multiple heat pipes 5 extendradially into corresponding bores 12 that extend away from the main wellbore 11. In this embodiment, the heat pipes 5 are arranged at threelevels, or distinct vertical positions, relative to the main well bore11, although more or fewer levels may be employed. Also, multiple heatpipes 5 may be deployed at each level, such as 3, 4, 6 or more heatpipes 5 per level. Alternately, the heat pipes 5 may be arrayed aroundthe main well bore 12 in random or irregular ways, e.g., to accommodateparticular geologic features of the well 1.

The mounting component 3 may support portions of the heat pipes 5 sothat the heat pipes are spaced from the heat exchanger 2 by a thermalgap, i.e., a space of desired size and thickness to create the thermalresistance through which heat is transferred from the heat pipes 5 tothe heat exchanger 2. In some embodiments, the thermal gap may be about¼ inch to 2 inches, although other suitable spacing may be employed.Thus, the heat pipes 5 may be out of direct contact with the heatexchanger so that a majority of heat transferred to the heat exchangeris through a thermal gap material 4 located in the thermal gap, e.g.,60%, 70%, 80%, 90%, 95% or more of heat transfer may occur via thethermal gap material 4. The thermal gap material 4 may have a relativelylow thermal conductivity, e.g., 0.5 to 12 W/m-K, at least as compared toa thermal conductivity of the material at the heat pipe 5 and/or heatexchanger 2 outer surface. As such, the thermal gap material 4 may meterheat transfer in a desired way, e.g., to allow the heat pipes 5 tooperate at an optimal working temperature as discussed more below. Thethermal gap material 4 may be or include a thermal grout, e.g., acement-like material that is designed to have a desired thermalconductivity, or other material such as water (including water withdissolved minerals, salts and/or other material). Thus, the thermal gapmaterial 4 may be a solid, liquid, semi-solid or other composite and maytransfer heat by conduction and/or by convection.

In some embodiments, to achieve meaningful heat harvesting rates, thegeothermal well should include a liquid pool or liquid-permeated porousrock so as to allow circulation of liquid within the volume of thegeothermal well 1. Heat removal from the geothermal resource by the heatexchanger 2, and particularly by the heat pipes 5, cools the liquid ofthe well 1 and increases its density. As the denser, cool liquid sinksdownwardly in the geothermal well 1, hotter liquid from below orelsewhere in or around the well 1 may move outwards and upwards tocreate large scale liquid circulation that may be necessary to deliversufficient heat to the heat pipes 5 and the heat exchanger 2 forharvesting. This liquid already present in the geothermal well mayitself, at least in part, function as a thermal gap material. Of course,other system 100 arrangements employing a lower heat harvesting rateneed not exploit a liquid or liquid-permeated substrate and/or employ alarge scale liquid circulation to operate properly. Also, although thisembodiment shows the heat pipes 5 extending away from the mountingcomponent 3 in a downward, curving arc, the heat pipes 5 may extend in astraight line and/or at any suitable angle(s) to the horizontal,including extending horizontally (or nearly so) in some embodiments.

FIG. 3 shows a cross sectional side view of the heat pipe mountingassembly of the FIG. 1 embodiment. The mounting component 3 (which inthis embodiment is shaped as a collar or sleeve) extends around at leastpart of the outer periphery of the heat exchanger 2 and positions theheat pipes 5 to define a gap between the heat pipes 5 and the heatexchanger 2. Note that the mounting component 3 may help establish asuitable gap between the heat pipes 5 and the heat exchanger 2 inportions of the heat pipes 5 positioned below or otherwise away from themounting component 3. The heat exchanger 2 in this embodiment includesan outer pipe 22 which carries a working fluid flow in a downwarddirection and an inner pipe 21 which carries an working fluid flow in anupward direction, e.g., heated working fluid may travel upwardly in theinner pipe 21 to the heat receiver 6. Thus, heat from the heat pipes 5may be transmitted to the working fluid flowing downwardly in the outerpipe 22 in this embodiment. Of course, the flow direction may bereversed, with relatively hot working fluid flowing upwardly in theouter pipe 22 and cooler working fluid flowing downwardly in the innerpipe 21.

In the gap between the mounting component 3/heat pipes 5 and the heatexchanger 2 is a thermal gap material 4, such as a thermal grout. As isexplained in more detail below, the thermal conductivity of the thermalgap material 4 may be lower than the thermal conductivity of themounting component 3 and heat pipes 5, and generally speaking, “meters”the flow of heat from the mounting component 3/heat pipes 5 to the heatexchanger 2 so that the heat pipe(s) 5 operate at an appropriate workingtemperature. In some embodiments, relatively little heat may betransmitted from the heat pipes 5 to the mounting component 3, so that abulk of heat transfer from the heat pipes 5 to the heat exchanger 2occurs directly from the heat pipes 5 to the thermal gap material 4 andthen to the heat exchanger 2. However, in other embodiments, asignificant amount of heat may be transferred from the heat pipes 5 tothe mounting component 3, which is then transferred from the mountingcomponent 3 to the thermal gap material 4. In this case, the mountingcomponent 3 may function as a heat spreader, i.e., assisting to transmitheat from a first surface area of a heat pipe having a first size to asecond surface area of the mounting component 3 that has a second sizegreater than the first size. As discussed more below, such heatspreading may assist in desired heat transfer to the heat exchanger, andto do so, a heat spreader may have a relatively high thermalconductivity, e.g., above 12 W/m-K. In some embodiments, a surface ofthe mounting component 3 that faces or otherwise thermally communicateswith the heat exchanger 2 may be configured to generally conform to theshape of the heat exchanger portion that receives heat from the thermalgap material 4, e.g., so that a conduction length across the thermal gapmaterial 4 may be maintained constant or otherwise controlled.

Many heat pipes are closed systems that rely on the counter flow of“liquid” and “vapor” phases of the “working fluid” within a sealedinterior volume of the pipe to transport heat along the pipe. At the hotor “evaporator” end, heat is absorbed by evaporating or boiling theliquid inside the heat pipe into its vapor phase while at the cold or“condenser” end the vapor phase condenses back into a liquid andreleases heat into the walls of the heat pipe. Vapor travelsautomatically from the hot end to the cold end by the pressuredifference caused by small temperature differences between the hot andcold ends. Other forces, such as gravity, are used to return thecondensed liquid from the cold to the hot end. Heat pipes that depend ongravity as the primary means to return condensed liquid from the coldend to the hot end are also called thermosiphons. Liquid and vapor flowin opposite directions in the heat pipe.

Because heat transport in heat pipes is mediated by the physicalmovement of liquid and vapor phases of the working fluid, the heattransport rate that can be achieved in heat pipes is limited by manymechanisms that apply to fluid flows. Some common limiting mechanismsare entrainment limit, flooding limit, sonic limit, boiling limit etc.,but in short, the heat transport limit of heat pipes is stronglydependent on the temperature of the working fluid inside the heat pipe.(The liquid and vapor phases inside a heat pipe exist in nearthermodynamic equilibrium so, for the purpose of this description, asingle temperature is used to refer to both phases.)

In accordance with an aspect of the invention, the thermal gap (i.e.,the conduction length or distance from the mounting component 3 (orother heat spreader) and/or the heat pipe 5 to the heat exchanger 2) andthe thermal gap material 4 in the gap between the heat spreader/heatpipe 5 and the heat exchanger 2 may be arranged to conduct heat suchthat the heat pipe(s) 5 operate at a desired working temperature, andenable substantial heat harvesting from the geothermal resource via theheat pipe(s) 5. For example, if the heat pipes 5 were to be placed indirect and very intimate thermal contact with the heat exchanger 2, theoperating temperature of the heat pipes would be low, close to the coldfluid temperature in the heat exchanger 2. Such cold heat pipesextending into the hot rock or other well 1 substrate could create a“high heat demand” from the well 1. However, at the “cold operatingtemperature,” the heat pipes 5 would have a “low heat transportcapability” and would not be able to carry the heat that would want toflow into the heat pipe 5 from the hot rock or other well substrate.

On the other hand, if the thermal connection between the heat pipes 5and the heat exchanger 2 is poor (such as if the heat pipes 5 are simplyinserted into the holes drilled into hot rock around a main well boreand not thermally coupled to the heat exchanger 2 in any particularway), the heat pipe temperature would be high, closer to the hightemperature of the hot rock. Such “hot heat pipes” would create a “lowheat demand” from the rock even though the heat pipes 5 would have a“high heat transport capability” due to their high operatingtemperature. In both the above scenarios, the heat pipes 5 would notprovide a suitably high heat harvesting rate, at least for someapplications. By providing a suitable thermal gap characteristics(conduction length and thermal conductivity) between the heat pipes5/heat spreader and the heat exchanger 2, the heat pipes 5 may operateat the desirable “in between” temperature such that a “relatively highheat demand” is placed on the hot rock and is well balanced against the“relatively high heat transport capability” of the heat pipes 5.

A further benefit of the “balanced high heat harvesting” rate of theheat pipes 5 is that more well fluid may be cooled to a higher densityto drive a larger total convective circulation in the geothermalresource. In this way, embodiments configured in accordance with anaspect of the invention may operate such that the heat content of thegeothermal well, or “reservoir,” is replenished at the same rate thatheat is harvested for efficient and cost effective energy productionover long term operation. Computer modeling of a geothermal well 1having its heat harvested using three thermal transfer components (i.e.,heat pipe/heat spreader/thermal gap material assemblies) positionedalong the length of a vertical heat exchanger arrangement like that inFIG. 2 have shown that the thermal transfer components are effective inincreasing convective flow in the geothermal well 1, and that additionalthermal transfer assemblies are expected to improve convective flow oversystems with fewer thermal transfer assemblies.

FIG. 4 shows a top cross sectional view of the mounting component 3along the line 4-4 in FIG. 1 in an illustrative embodiment. In thisexample, the mounting component 3 has the form of a continuous annularcollar or sleeve that extends around the heat exchanger 2. Also, in thisembodiment, four heat pipes 5 pass through openings in the wall of thecollar 3, thereby thermally coupling the heat pipes 5 to the collar 3and allowing the collar 3 to function as a heat spreader. Of course,fewer or more heat pipes 5 may thermally couple with the mountingcomponent 3 if desired. Other configurations for a mounting component 3are possible, such as that shown in FIG. 5 in which the mountingcomponent 3 includes four “shoes” or curved plates that each thermallycouple with a corresponding heat pipe 5. The shoes may be physicallyattached to each other, or not, as desired, and may be thermally coupledwith each other, or not. Note also that the mounting component 3 neednot necessarily be thermally coupled with a heat pipe 5, but instead maymechanically support the heat pipe 5 in a desired orientation anddistance from a heat exchanger 2, e.g., to define a desired thermal gap.Thus, the mounting component 3 need not function as a heat spreader orotherwise transmit significant heat from the heat pipes 5 to the thermalgap material 4. Also, a heat spreader may be used in conjunction with amounting component 3 that serves to physically support the heat pipe(s)5, but does not function as a heat spreader.

While the surface area of the heat pipes 5 and/or heat spreader is animportant design consideration when arranging the system to operate suchthat the coupled heat pipe(s) 5 function at a desired workingtemperature, the distance between the heat pipes 5 and/or heat spreaderand the heat exchanger 2 (or conduction length) may be another importantfactor. As noted above, the surface of the heat pipes 5 or heat spreaderthat faces the heat exchanger 2 may be shaped or contoured to match orconform with a counterpart surface of the heat exchanger 2. Thus, if theheat exchanger 2 has a cylindrically-shaped outer surface, the mountingcomponent 3 or other heat spreader may include a correspondingcylindrically-shaped inner surface that faces the heat exchanger 2.Alternately, if the heat exchanger 2 includes a dimpled, grooved, orother shaped surface, the mounting component 3 or other heat spreadermay have a corresponding shape. This arrangement may help maintain athermal gap between the heat spreader and the heat exchanger 2 at aconstant or otherwise known value, e.g., to help ensure that aconduction length of the thermal gap material 4 is constant or otherwiseknown across the thermal junction. In some embodiments, the distancebetween the mounting component 3 and the heat exchanger 2 may be definedin different ways, such as by standoffs, tabs, pins, annular rings orother structures that extend from the mounting component 3 toward theheat exchanger 2. These gap-defining elements may help ensure that thereis a minimum (or maximum) distance between the mounting component 3/heatpipes 5 and the heat exchanger 2. The gap-defining elements may be madesmall enough or otherwise configured to contribute minimally to heattransfer between the heat spreader and the heat exchanger, oralternately, these gap-defining spacer elements may function as anon-trivial part of the heat transfer. If so, the gap between the heatspreader and the heat exchanger (conduction length), the thermalconductivity of the thermal gap material and/or the surface area of theheat spreader (i.e., the surface area facing the heat exchanger or thatmeaningfully contributes to heat transfer to the heat exchanger) may bedesigned to provide the desired heat transfer rate along with thegap-defining elements.

Deployment of a thermal gap material 4 in the space or gap between themounting component 3/heat pipes 5 and the heat exchanger 2 may be donein a variety of ways. For example, the thermal gap material 4 may takethe form of a flowable grout that can flow when deployed, and then mayoptionally harden after deployment. The grout may be pumped into placeafter the mounting component 3 and heat exchanger 2 are positionedrelative to each other in the well 1, or may be applied to the heatexchanger 2 and/or to the mounting component 3 prior to positioning ofthe elements relative to each other. In other embodiments, the thermalgap material 4 may be present in the well 1 at or after the time ofinstalling the heat exchanger 2 and/or heat pipes 5. For example, thethermal gap material 4 may be or include water (such as brine) in thewell 1 that occurs naturally or is introduced, e.g., by pumping thewater into the well 1. Thus, in some embodiments, the thermal gapmaterial may include a liquid that can flow so as to accommodateconvective heat transfer, as well as conductive heat transfer, betweenthe heat pipes 5 and the heat exchanger 2.

FIG. 6 shows an illustrative embodiment in which thermal gap material 4is contained in one or more reservoirs 42 as introduced into the well 1.In FIG. 6, the portion of the image to the left of the heat exchanger 2shows the thermal gap material 4 before deployment, while the portion ofthe image on the right of the heat exchanger 2 shows the thermal gapmaterial 4 after deployment. A shaped charge (e.g., an explosivedevice), a plunger or piston, a clamp or other mechanism 41 may deformthe reservoir 42, or otherwise force the thermal gap material 4 to flowfrom the reservoir 42 into the gap between the heat exchanger 2 and theheat pipes 5 and/or heat spreader. FIG. 7 shows another illustrativeembodiment in which the mounting component 3 has an attached thermal gapmaterial reservoir 42 that includes one or more ports 43 arranged toexpel thermal gap material 4 in the gap when the thermal gap material iscaused to flow. In this embodiment, the reservoir 42 that is squeezed bya clamp 41 that includes a collar or sleeve with a conical lower surfacethat bears on the reservoir 42 as the collar is moved downwardly towardthe mounting component 3. (As in FIG. 6, the portion of the image to theleft of the heat exchanger 2 in FIG. 7 shows the thermal gap material 4before deployment, while the portion of the image on the right of theheat exchanger 2 shows the thermal gap material 4 after deployment.) Ofcourse, other arrangements are possible for deploying a thermal gapmaterial 4, such as a pump that pumps thermal gap material 4 via aconduit to the gap between a heat pipe and the heat exchanger. Also,while in the FIGS. 6 and 7 embodiments the thermal gap material 4 flowsgenerally downwardly and radially inwardly, the material 4 may flow inany suitable way, e.g., the material 4 may flow only radially inwardlyfrom one or more reservoirs to a thermal gap between a heat spreaderand/or heat pipe and the heat exchanger.

In accordance with an aspect of the invention, one or more heat pipesmay be engaged with a mounting component so that the assembled heatpipes and mounting component may be lowered into a well bore and theheat pipes deployed into corresponding well bores. For example, FIG. 8shows an illustrative arrangement in which four heat pipes 5 areattached to a mounting component 3 that includes upper and lower collars3 a, although more collars 3 a may be used if desired. The upper andlower collars 3 a may be spaced from each other, e.g., at a distance of5, 10, 20 or more feet along the length of the heat pipes 5, which inthis embodiment may be up to 120 to 300 feet long or more. In otherembodiments, the upper and lower collars 3 a may be replaced with asingle collar that spans along a desired length of the heat pipes 5,e.g., 5, 10 or 20 feet or more in length. The single collar 3 a may bearranged as a cylindrical shell, e.g., to prevent flow into/out of aspace within the collar 3 a, or may have openings to permit flow. In theillustrated embodiment, the portion of the heat pipes 5 between thecollars 3 a are exposed and a gap between the heat pipes 5 and a heatexchanger 2 positioned within the heat pipes (not shown) may be definedby the collars 3 a. Given the relatively long length of the heat pipes 5positioned adjacent the heat exchanger 2, a majority of heat transferredfrom the heat pipes 5 to the heat exchanger 2, e.g., 90%, 95% or more,may be transmitted directly from the heat pipes 5 to the heat exchangervia a thermal gap material 4. Thus, the collars 3 a may play a minorrole in heat transfer in this embodiment, but in other embodiments mayserve to transfer a much larger amount of heat.

FIG. 9 shows a cross sectional view of a collar 3 a along the line 9-9in FIG. 8. This embodiment is similar to that shown in FIG. 4, with onedifference being that the collar 3 a (a mounting component) engages theheat pipes 5 at an outer surface of the collar 3 a. Also, the collar 3 ais shown including one or more spacer elements 34, such as a protrusion,rib, pin, etc. that extends radially inwardly from an inner side of thecollar 3 a. The spacer elements 34 may assist in defining a suitablethermal gap between the heat pipes 5 and the heat exchanger 2, not onlyin areas at or near the collar 3 a, but also for portions of the heatpipes 5 between the upper and lower collars 3 a. Note also that the heatpipes 5 in this embodiment each include a heat spreader 51 in the formof a sleeve 51 that is positioned over the outer surface of the heatpipe 5. In one embodiment, the heat pipe 5 may be formed by a coppertube or pipe, and the heat spreader 51 may be arranged as a stainlesssteel sleeve that extends over a portion of, or the entire, heat pipe 5.The heat spreader 51 may serve to not only increase a surface area forheat transfer from the heat pipe 5, but also may provide the heat pipe 5with mechanical support (e.g., to resist crushing and/or bursting of thepipe 5), corrosion resistance, and/or other characteristics. The collars3 a may engage the heat spreaders 51 by welding, an adhesive, clamping,an interference fit or other suitable arrangement.

In accordance with an aspect of the invention, the assembly may includeone or more anti-buckling supports which may help support the heat pipesbefore and/or during deployment in the well 1. For example, as shown inFIG. 8, anti-buckling supports 3 c may be attached to the heat pipes 5below the collars 3 a, e.g., to help keep the heat pipes 5 from bendingor buckling during deployment or to otherwise support the heat pipes 5.A distance between each anti-buckling supports 3 c and an adjacentanti-buckling support 3 c or collar 3 a may be arranged to be equal toor less than a maximum unsupported length of heat pipe for loading incompression without buckling. So, for example, if a particular force isneeded to be applied to the heat pipes 5 for deployment of the heatpipes into the well 1, one or more anti-buckling supports 3 c may beprovided at suitable locations along the length of the heat pipes 5 tohelp prevent buckling of the pipes 5 during deployment. The heat pipes 5may be attached to the anti-buckling supports 3 c in a way thatmaintains the anti-buckling supports 3 c in place relative to the heatpipes 5 during deployment of the heat pipes 5 into the well 1, but thatreleases the heat pipes 5 relative to the anti-buckling supports 3 conce a force exerted on the heat pipes 5 relative to the anti-bucklingsupport 3 c exceeds a threshold. For example, with reference to FIG. 3,as the collars 3 a and heat pipes 5 are moved downwardly in the mainwell bore 11, the heat pipes 5 may be deployed into their respectivebores 12 of the well 1. As the anti-buckling supports 3 c reach thepoint where the heat pipes 5 exit the main well bore 11, theanti-buckling supports 3 c may disengage from the heat pipes 5, e.g.,via a frangible or other releasable connection.

For example, FIG. 10 shows one illustrative embodiment of ananti-buckling support 3 c. Heat pipes 5 may be engaged at openings 37 ofheat pipe engagement portions 35, and the heat pipes may be fixed to theportions 35 by welding, solder, an adhesive, a clamp, or otherarrangement. Frangible links 36 may permit the engagement portions 35and heat pipes 5 to disengage from a central portion 38 of theanti-buckling support 3 c, e.g., when a suitable force is applied to theheat pipes 5 relative to the support 3 c whether in shear and/ortension. As will be understood, and is discussed more below, the heatpipes 5 may be releasably attached to the anti-buckling support(s) 3 cin other ways, such as by an adhesive that breaks or fails in thepresence of a suitable force, rubber sleeves on the heat pipes 5 thathold the anti-buckling supports 3 c in place relative to the heat pipes5, but allow the heat pipes 5 move along their length relative to theanti-buckling supports in the presence of a suitable force, and others.

Another feature shown in FIG. 10 is that the anti-buckling support 3 cmay be arranged with a clam shell or other suitable configuration thatallows the support 3 c to be assembled around an existing drill stringand/or heat exchanger 2. That is, when installing a thermal energyharvester in a well 1, a drill string used to form one or more bores 11,12 may be in place when the heat pipes 5 and mounting component(s) 3 areinstalled. By making the anti-buckling support 3 c and/or the collars 3a in a clam shell configuration (see FIG. 11 regarding a collar 3 ahaving a clam shell arrangement), the support 3 c and/or collars 3 a maybe assembled around a drill string or heat exchanger 2. That is, boltsor other fasteners used to secure the support 3 c and/or collar 3 asections together may be removed so the sections can be placed aroundthe drill string or heat exchanger 2 and then fastened together. FIG. 12shows a cross sectional view along the line 12-12 in FIG. 8 and showsanother illustrative embodiment for an anti-buckling support 3 c. Inthis embodiment, the heat pipes 5 are engaged by sleeve-shapedengagement portions 35 of the anti-buckling support 3 c as opposed to aplate shaped element as in FIG. 10. The frangible links 36 are formed asrib-shaped elements that extend along a length of the heat pipes 5,although other arrangements are possible. FIG. 12 also shows anembodiment of a collar 3 a like that in FIG. 9, except that in FIG. 12the collar 3 a is formed in two sections. The sections may be joinedtogether by bolts or other fasteners, welding, etc. This embodiment alsoincorporates a spacer element 34 at the joint between the two collarsections.

In accordance with another aspect of the invention, a heat pipedeployment system may include a heat pipe guide, or “kicker,” that helpsto guide the heat pipe(s) into their respective bore in a well. Forexample, the heat pipe guide may be arranged in the main well bore andinclude a flared or curved guide channel for one or more heat pipes. Theguide channel may engage a heat pipe, e.g., at the distal end, and guidethe heat pipe into a radially extending bore. The heat pipe guide mayalso be used to guide a tool that forms radially extending heat pipebores, such as a rotary drilling tool, high pressure jet device, etc.For example, FIG. 13 shows an assembly including four heat pipes 5,upper and lower collars 3 a, an anti-buckling support 3 c and a heatpipe guide 3 b. FIG. 14 shows a close up view of the heat pipe guide 3b. The guide 3 b may include a plurality of guide grooves 39, e.g., onefor each heat pipe 5, that is curved or otherwise arranged to guidemovement of the distal end of the heat pipes 5 into a correspondingradial bore 12 as the heat pipes 5 are lowered into a well 1. The radiusof curvature of the grooves 39 may be any suitable distance, such as10-30 ft. Although in this embodiment, the guide 3 c is shown arrangedas a solid part with no through hole, e.g., through which a heatexchanger 2 may pass, the guide 3 c may be arranged to receive a drillstring, heat exchanger 2 or other element in an opening in the center ofthe guide 3 c. Moreover, the guide 3 b may be made in a clam shellconfiguration or other multi-part arrangement that permits assembly ofthe guide 3 b around a drill string. In some embodiments, the guide 3 bmay be used to guide a drill bit or other device that is used to formthe bores 12 for heat pipes. This may help ensure that the grooves 39are aligned with corresponding bores 12 for insertion of the heat pipes5. Alternately, the bores 12 may be made without the use of the guide 3b, and the grooves 39 may be suitably aligned with the bores 12 prior toheat pipe insertion.

In accordance with another aspect of the invention, a portion of amounting component, anti-buckling support and/or heat pipe guide mayform part of the heat exchanger. That is, in the embodiments above, aportion of the mounting component is adjacent to, and spaced from, aportion of the heat exchanger and a thermal gap material serves toconduct heat from the heat spreader to the heat exchanger. However, insome embodiments, one or more portions of the heat pipe deploymentsystem may function as part of the heat exchanger, and any thermal gapor other thermal link between heat pipes and the heat exchanger may beprovided as part of the system. For example, FIG. 15 shows an embodimentin which a mounting component 3 a, heat pipe guide 3 b, andanti-buckling support 3 c serve as part of the heat exchanger 2. In thisembodiment, the heat exchanger 2 includes an inner pipe 21 that extendsdownwardly within an outer pipe 22. The inner pipe 21 carries coolworking fluid to near a bottom of the well 1, and heated working fluidis conducted upwardly in the space between the inner and outer pipes 21,22. Although the inner pipe 21 extends downwardly to near a bottom ofthe well 1, the outer pipe 22 is connected to the mounting component 3a, and from that point downward, the assembly of the mounting component3, anti-buckling support 3 c and heat pipe guide 3 b defines the “outerpipe” of the heat exchanger 2. To contain the working fluid in the heatexchanger 2, the portions 3 a, 3 b and 3 c may be joined together todefine a water tight conduit around the inner pipe 21, e.g., by the useof o-rings, adhesives, threaded connections, clamps and/or othercomponents. Any thermal gap provided between the heat pipes 5 and theworking fluid in the heat exchanger 2 may be provided as part of theportions 3 a, 3 b and 3 c.

FIG. 16 shows the heat spreader arrangement of FIG. 15 in an “expanded”state prior to deployment in the FIG. 12 configuration. That is, themounting component 3 may include an upper portion 3 a that is fixed tothe heat pipes 5 and a lower portion 3 b that includes heat pipe guidesto guide deployment of the heat pipes 5 into corresponding bores 12 inthe well 1 as the upper portion 3 a is moved toward the lower portion 3b. However, this embodiment additionally includes one or more middleportions 3 c (e.g., an anti-buckling portion) that may be attached tothe heat pipes 5, e.g., to help keep the heat pipes 5 from bending orbuckling during deployment or to otherwise support the heat pipes 5. Adistance L between each middle portion 3 c and an adjacent middleportion 3 c, upper portion 3 a or lower portion 3 b may be arranged tobe equal to or less than a maximum unsupported length of heat pipe forloading in compression without buckling. So, for example, if aparticular force is needed to be applied to the heat pipes 5 by theupper portion 3 a for deployment, one or more middle portions 3 c may beprovided at a suitable length L along the heat pipes 5 to help preventbuckling of the pipes 5 during deployment. The heat pipes 5 may beattached to the middle portions 3 c in a way that maintains the middleportions 3 c in place relative to the heat pipes 5 during deployment ofthe heat pipes 5 into the well 1, but that releases the heat pipes 5relative to the middle portion 3 c once the middle portion reaches thelower portion 3 b or an adjacent middle portion 3 c below. For example,as the upper portion 3 a is moved toward the lower portion 3 b in thewell 1, the heat pipes 5 will be deployed into their respective bores 12of the well 1 and the middle portion 3 c will move downwardly toward thelower portion 3 b. When the middle portion 3 c contacts the lowerportion 3 b, a connection between the middle portion 3 c and the heatpipes 5 will be released so that the heat pipes 5 can slide relative tothe middle portion 3 c. For example, the heat pipes 5 may be joined tothe middle portion 3 c by a frangible joint (e.g., a tin solderedconnection, an adhesive, etc.) that is capable of supporting the middleportion 3 c on the heat pipes 5, but that breaks away once the middleportion 3 c contacts the lower portion 3 b. This allows the upperportion 3 a to be moved downwardly, further deploying the heat pipes 5in the well 1 until the upper portion 3 a meets the middle portion 3 c.

As a result, the portions 3 a, 3 b, 3 c may be stacked onto each otherwhen the heat pipes 5 are fully deployed into the well 1. As mentionedabove, the portions 3 a, 3 b, 3 c may be joined together, as shown inFIG. 17, to form a water tight seal at an inner portion such that theportions 3 a, 3 b, 3 c may define an outer conduit of the heat exchanger2. For example, as shown in FIG. 18, the portions 3 a, 3 b, 3 c mayengage each other such that one portion (the middle portion 3 c in thisexample) includes a protruding conical section that engages with aconical receiver opening in the other portion (the lower portion 3 b inthis example). These conical sections may be tightly forced together,forming a water tight seal, by threaded engagement, one or more clamps,etc. The conical engagement surfaces of the middle portion 3 c and thelower portion 3 b (a male conical engagement surface of the middleportion 3 c, and female engagement surface of the lower portion 3 b) mayalso help align the portions 3 c, 3 b relative to each other in a radialdirection. For example, if the heat pipes 5 and middle portion 3 c arelowered to the lower portion 3 b as shown in FIG. 18, the middle andlower portions 3 c, 3 b may need to be aligned with each other radiallyto form a suitable water tight joint. In addition, or alternately, theheat pipe 5 ends may need to be aligned with guide grooves in the lowerportion 3 b, and the radial alignment feature provided by the conicalengagement surfaces may also serve to align the heat pipes 5 with theguide grooves.

Furthermore, the middle and lower portions 3 c, 3 b may include featuresthat help align the portions in a rotational direction. For example, thelower portion 3 b may include two heat pipe guide grooves located at 180degrees from each other. To help align the heat pipes 5 with theirrespective guide grooves, the conical engagement surfaces may includecomplementary slots and protrusions that interact to align the middleand lower portions 3 c, 3 b rotationally. For example, the lower portion3 b may include one or more V-shaped slots in the conical engagementsurface (with the wide end of the “V” facing upwardly) that receivedcomplementary V-shaped protrusions on the conical engagement surface(with the narrow end of the “V” facing downwardly) of the middle portion3 c. The complementary slots and protrusions may engage with each otherto rotate the middle and lower portions 3 c, 3 b relative to each other,as necessary, so that the heat pipe 5 ends are suitably located relativeto the guide grooves of the lower portion 3 b. Those of skill in the artwill appreciate that other engagement surface arrangements are possibleto provide radial and/or rotational alignment of the middle and lowerportions 3 c, 3 b. Moreover, such alignment features may be providedbetween adjacent middle portions 3 c, and/or between a middle portion 3c and the upper portion 3 a.

FIG. 19 shows a perspective view and FIG. 20 shows a cross sectionalview of the upper portion 3 a along the line 20-20 in FIG. 15. As can beseen, the inner pipe 21 extends within an inner wall 31 of the upperportion 3 a. The inner wall 31 is joined to the outer pipe 21 of theheat exchanger 2, and so forms an outer conduit of the heat exchanger 2in this embodiment. An outer wall 32 is also provided, but may functiononly as a well bore liner pipe. As such, the outer wall 32 may be madeof a less robust or corrosion resistant material than other parts of theupper portion 3 a since the outer wall 32 may be needed only duringinstallation of the upper portion 3 a, e.g., to prop up the walls of awell hole. The upper portion 3 a couples to four heat pipes 5 in thisembodiment, though more or fewer heat pipes 5 could be used. The upperportion 3 a includes saddles 33 that join to a respective heat pipe 5,and may provide physical support for the pipe 5 relative to the upperportion 3 a. The saddles 33 may be arranged in different ways, such asby a block of material having a hole formed in it, as a two-partclamshell device that clamps onto the heat pipe outer surface, a platewith a hole formed in it, etc. The saddles 33 may be directly joined tothe inner wall 31, and the joint may be arranged (e.g., of suitablecross sectional area) to provide a desired (e.g., to create a suitablethermal gap) thermal coupling between the heat pipe 5 and the inner wall31. For example, if the heat pipe 5 is directly in contact with thesaddle 33, a joint between the saddle 33 and the inner wall 31 may besuitably sized (e.g., of suitable cross sectional area and joint thermalconductivity) to provide a suitable thermal coupling between the heatpipe 5 and the inner wall 31 to balance the heat pipe temperature andthe heat harvesting rate as earlier described. Alternately, the junctionof the saddles 33 to the inner pipe 31 may be of such relatively smallcross sectional area and/or low thermal conductivity as to beineffective in transferring heat to the working fluid, and instead athermal gap material 4, e.g., filling a space between the inner andouter walls 31, 32, provides the bulk of thermal coupling between theheat pipe 5 and the inner wall 31, similar to that in the FIG. 3embodiment.

In another embodiment, if the saddles 33 are joined to the inner wall 31with higher than desired thermal transfer capacity, a junction betweenthe saddles 33 and the heat pipes 5 may be arranged to provide thedesired thermal junction. For example, as shown in the close up view ofthe saddle 33 at the 9 o'clock position in FIG. 20, a joint between theheat pipes 5 and the saddles 33 may include a thermal gap material 4that provides the desired thermal coupling between the heat pipes 5 andthe inner wall 31. This arrangement may have the advantage of beingconstructed outside of the well 1, e.g., a thermal gap material 4 suchas a grout, polymer material, etc., may be provided between the heatpipe 5 outer surface and the saddle 33 when the heat pipes 5 areattached to the saddle 33. This may allow for easier, less expensive andpossibly more accurate control of the thermal gap thickness between theheat pipe 5 and the saddle 33.

FIG. 21 shows a cross sectional side view of the upper section 3 a ofthe FIG. 15 embodiment and illustrates that the inner wall 31 of theupper section 3 a may be joined to the outer pipe 22 of the heatexchanger 2. This joint may be formed in any suitable way, such as bywelding, a threaded connection, a clamp, etc. Also, this view shows asaddle 33 arrangement in which the saddle 33 is joined directly to theinner wall 31 only, e.g., by brazing, welding, an adhesive, etc.

FIGS. 22-25 show different saddle arrangements for connecting a heatpipe 5 to the inner wall 31 or other portion of a mounting component 3.Note that all, or at least some, of these saddle arrangements may beused with a middle portion (or anti-buckling support) 3 c of a mountingcomponent 3. In FIG. 22, the saddles 33 are arranged to have two parts33 a, 33 b that are joined together at a seam 33 c that is orientedradially relative to the inner wall 31. Thus, to mount a heat pipe 5 tothe inner wall 31, a first part 33 a or 33 b may be attached to theinner wall 31, e.g., via welding at a joint 33 d. With the heat pipe 5positioned against the first part 33 a or 33 b, the other part may bepositioned adjacent the heat pipe 5 and attached to the inner wall 31 tocapture the heat pipe 5 in place. FIG. 23 shows a similar arrangement tothat of FIG. 22, except that the saddle portions 33 a, 33 b do notextend completely around the heat pipe 5. In fact, the saddle 33 neednot surround all or part of the heat pipe 5, but may engage just aportion of the heat pipe, as shown for example in FIG. 24. In anarrangement like that in FIG. 24, the heat pipe 5 may be attached to thesaddle 33 by welding, brazing, an adhesive, or other suitablearrangement. In fact, a heat pipe 5 may be secured to any type ofsaddle, including those of FIGS. 22 and 23, by welding, brazing, anadhesive or other arrangement, and the connection of the heat pipe 5 tothe saddle 33 may be made permanent (e.g., so the heat pipe 5 will notdetach from the saddle 33 without damage or deformation of the heat pipe5 or saddle 33) or made frangible or otherwise releasable. For example,a heat pipe 5 may be attached to a saddle 33 so that the heat pipe 5 candetach from the saddle 33 in certain conditions, such as where more thana threshold level of force is applied to the heat pipe 5 relative to thesaddle 33. However, one possible advantage of attaching a heat pipe 5 toa saddle 33, yet allowing the heat pipe 5 to freely slide, e.g., likethat in FIGS. 22 and 23, is that the heat pipe 5 may be attached to theinner wall 31 yet allowed to slide along its length relative to thesaddle 31, which may be desirable in circumstances where a temperatureof the heat pipe may cycle between high and low temperatures. Thisfeature may also be exploited when used with a middle portion(anti-buckling support) 3 c of the mounting component 3. For example,the heat pipe 5 may be passed through the opening of a saddle 33 so thatthe heat pipe 5 can slide freely relative to the saddle 33. To supportthe middle portion 3 c relative to the heat pipe 5, rubber sleeves maybe positioned on the heat pipe 5 above and below the saddle 5 thatengage the heat pipe 5 with a suitable amount of friction to support theweight of the middle portion 3 c, but allow the heat pipe 5 to sliderelative to the saddle 33 with forces over a threshold level.Alternately, the rubber sleeves may be replaced with a frangible orreleasable connection (e.g., a brazed or solder joint, adhesive, etc.),a break-away collar or other component that releases the heat pipe 5from the saddle 33 when the force on the heat pipe 5 relative to thesaddle 33 exceeds the threshold level. Thus, the arrangement of FIG. 24may also be used with a middle portion 3 c, and if so, a connection ofthe heat pipe 5 to the saddle 33 may be made frangible so as to give wayonce force over a threshold level is applied to the heat pipe 5 relativeto the saddle 33. One type of frangible connection may be provided by atin soldered joint, an adhesive of suitable bonding strength, etc.

FIG. 25 shows another arrangement similar to that in FIG. 22, exceptthat the seam 33 c between the saddle portions 33 a, 33 b is orientedcircumferentially rather than radially as in FIG. 22. This may allow afirst portion 33 a of the saddle 33 to be attached to the inner wall 31,and the second portion 33 b to be attached to the first portion 33 a tocapture the heat pipe 5. The first and second portions 33 a, 33 b mayengage in any suitable way, such as by welding, one or more screws orother fasteners, etc. In one arrangement, the first and second portions33 a, 33 b may be joined by a hinge at one seam portion 33 d, so thatthe second portion 33 b may be pivoted to an open position to allow aheat pipe 5 to be positioned in a receiving groove of the first portion33 a. Thereafter, the second portion may be pivoted to a closed positionand secured to the first portion 33 a to capture the heat pipe 5. Aswith other saddle embodiments, the heat pipe 5 may be secured to thesaddle via a permanent or frangible connection as well.

While in the embodiments above, a thermal gap material or othercomponent is provided to control (e.g., limit) heat transfer between aheat pipe and a working fluid of the heat exchanger 2, such material isnot always required, especially when the well temperature is low. Forexample, FIG. 26 shows an embodiment in which a condensing portion of aheat pipe 5 extends through the inner wall 31 to directly contact theworking fluid in the heat exchanger 2. (The opening in the inner wall 31through which the heat pipe 5 passes may be sealed closed, e.g., weldedor brazed, to prevent leakage of working fluid.) The condensing portionof the heat pipes 5 may be a relatively long length, e.g., 5 meters ormore, and may extend from near a bottom end of the heat exchanger 2upwardly. A similar result may be achieved as well by having the heatpipes in direct thermal contact with the inner wall 31, such as byhaving the heat pipes 5 in direct contact with saddles 33, that are indirect contact with the inner wall 31, where the saddles 33 and the wall31 are formed of, or include, a highly thermally conductive material,such as steel. As noted above, such an arrangement may reduce thetemperature and the heat transport capability of the heat pipes, butsuch a result may be acceptable for some applications.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.

The use of “including,” “comprising,” “having,” “containing,”“involving,” and/or variations thereof herein, is meant to encompass theitems listed thereafter and equivalents thereof as well as additionalitems.

It should also be understood that, unless clearly indicated to thecontrary, in any methods claimed herein that include more than one stepor act, the order of the steps or acts of the method is not necessarilylimited to the order in which the steps or acts of the method arerecited.

While aspects of the invention have been described with reference tovarious illustrative embodiments, such aspects are not limited to theembodiments described. Thus, it is evident that many alternatives,modifications, and variations of the embodiments described will beapparent to those skilled in the art. Accordingly, embodiments as setforth herein are intended to be illustrative, not limiting. Variouschanges may be made without departing from the spirit of aspects of theinvention.

1. A geothermal heat harvesting system, comprising: a heat exchangerarranged to receive heat from a geothermal well for transfer to a heatreceiving component; and one or more heat pipes arranged in the well totransfer heat from the well to the heat exchanger, the one or more heatpipes each having an evaporator section positioned within the geothermalwell and distant from the heat exchanger and a condenser sectionpositioned adjacent the heat exchanger.
 2. The system of claim 1,further comprising: a thermal gap material positioned in a thermal gapbetween the condenser section of the one or more heat pipes and the heatexchanger, the thermal gap material providing a thermal coupling betweenthe one or more heat pipes and the heat exchanger such that a desiredtemperature drop is achieved between the one or more heat pipes and theheat exchanger when heat is transferred via the thermal gap material,the thermal gap material having a thermal conductivity less than about12 W/m-K.
 3. The system of claim 2, wherein a conduction length of thethermal gap and the thermal conductivity of the thermal gap material arearranged to define a working temperature for the at least one heat pipe.4. The system of claim 2, wherein the thermal gap material includesliquid water or geothermal brine and has a thermal conductivity of about0.6 W/m-K.
 5. The system of claim 2, further comprising a heat spreaderbetween the one or more heat pipes and the thermal gap material and thatis in direct thermal contact with the one or more heat pipes and thethermal gap material.
 6. The system of claim 5, wherein the heatspreader is metal and/or has thermal conductivity over 12 W/m-K.
 7. Thesystem of claim 5, wherein the heat spreader includes a sleevepositioned over the heat pipe.
 8. The system of claim 5, wherein theheat spreader has a cylindrical shape, a partial cylindrical shellconfiguration, is a sleeve and/or is a plate.
 9. The system of claim 1,wherein the one or more heat pipes includes a plurality of heat pipesthat are arranged around the heat exchanger at a vertical level in thewell.
 10. The system of claim 9, wherein the one or more heat pipesincludes a plurality of heat pipes that are arranged around the heatexchanger at multiple vertical levels in the well.
 11. The system ofclaim 1, wherein the one or more heat pipes each have a length of 40 to300 feet.
 12. The system of claim 1, wherein the condenser section ofthe heat pipes is aligned along a length of the heat exchanger.
 13. Thesystem of claim 1, wherein the condenser section of the heat pipes isuniformly spaced from the heat exchanger along a length of the condensersection of 2 to 20 feet.
 14. The system of claim 1, wherein theevaporator section of the one or more heat pipes extends radially awayfrom the heat exchanger from 20 to 300 feet.
 15. The system of claim 1,further comprising a collar engaged to the one or more heat pipes, thecollar configured to receive the heat exchanger at an inner side of thecollar and to position the one or more heat pipes from the heatexchanger so as to define a thermal gap between the one or more heatpipes and the heat exchanger.
 16. The system of claim 1, furthercomprising a heat receiving component that includes a heat exchangefluid, one or more conduits to conduct a heat exchange fluid, a thermalstorage device, a thermal storage medium, and/or one or morethermoelectric or other power conversion devices.
 17. The system ofclaim 1, wherein the one or more heat pipes includes a thermosiphon, aloop thermosiphon, a pulsating heat pipe, and/or an osmotic heat pipe.18. A heat pipe and mounting component apparatus for use with a heatexchanger in harvesting geothermal heat, comprising: one or more heatpipes each having two end portions and an elongated central portion; anda mounting component arranged and dimensioned to engage with an endportion of the one or more heat pipes and to position the end portionwithin a specified distance of a perimeter of the heat exchanger todefine a thermal gap between the one or more heat pipes and the heatexchanger to be filled by a thermal gap material that thermally couplesthe one or more heat pipes to the heat exchanger.
 19. The apparatus ofclaim 18, further comprising the thermal gap material positioned in thegap between, and thermally coupling, the heat exchanger and the one ormore heat pipes.
 20. The apparatus of claim 19, wherein a size of thegap and a thermal resistance of the thermal gap material are configuredto permit the one or more heat pipes to operate at an optimal heat pipeworking temperature for use in harvesting geothermal energy.
 21. Theapparatus of claim 20, wherein the optimal heat pipe working temperatureis higher than the temperature of the heat exchanger by an amountbetween 10% and 40% of the temperature difference from the heatexchanger to the geothermal resource.
 22. The apparatus of claim 18,wherein the thermal gap material has a thermal conductivity of 0.5 to 12W/m-K that is less than a thermal conductivity of the mountingcomponent.
 23. The apparatus of claim 18, wherein the mounting componenthas a contact area with the one or more heat pipes and a thermalconductivity selected to promote heat spreading from the one or moreheat pipes that are thermally coupled to the mounting component.
 24. Theapparatus of claim 23, further comprising the thermal gap material whichincludes water.
 25. The apparatus of claim 18, wherein the mountingcomponent has a surface area facing the heat exchanger that is largerthan a surface area presented by the at least one heat pipe to the heatexchanger.
 26. The apparatus of claim 25, wherein the surface area ofthe mounting component facing the heat exchanger is at least 1 to 10times the surface area presented by the at least one heat pipe to theheat exchanger.
 27. The apparatus of claim 18, wherein the mountingcomponent includes a collar arranged to extend around the perimeter ofthe heat exchanger, the collar including a plurality of spacer elementsextending radially inwardly from the collar to define, at least in part,the gap between the one or more heat pipes and the heat exchanger. 28.The apparatus of claim 18, wherein the mounting component includes anupper collar and a lower collar, the upper and lower collars beingspaced from each other and having the one or more heat pipes fixed tothe upper and lower collar and arranged to define a gap between the oneor more heat pipes and the heat exchanger in areas between the upper andlower collars.
 29. The apparatus of claim 28, further comprising ananti-buckling support engaged with the one or more heat pipes below thelower collar and arranged to move relative to the one or more heat pipesin the presence of a force over a threshold.
 30. The apparatus of claim18, wherein the one or more heat pipes each include an evaporatorsection and a condenser section, the one or more heat pipes beingthermally coupled with the mounting component at the condenser section.31. The apparatus of claim 18, further comprising a heat exchangerpositioned adjacent the mounting component, wherein the thermal gap ispresent between the heat exchanger and the mounting component.
 32. Theapparatus of claim 31, further comprising a thermal gap materialpositioned between the mounting component and the heat exchanger, thethermal gap material having a thermal conductivity that is less than athermal conductivity of the mounting component.
 33. The apparatus ofclaim 32, wherein the thermal gap material includes liquid water. 34.The apparatus of claim 18, further comprising a heat pipe guideincluding a guide channel to guide movement of a heat pipe into a borein a geothermal well.
 35. A geothermal heat harvesting system,comprising: a heat exchanger arranged to transfer heat from a geothermalwell to a heat receiving component; one or more heat pipes arranged inthe well to transfer heat from the well to the heat exchanger, the oneor more heat pipes having an evaporator section and a condenser section;and a thermal gap material positioned in a thermal gap between the oneor more heat pipes and the heat exchanger, the thermal gap materialproviding a thermal coupling between the one or more heat pipes and theheat exchanger such that more than 60% of heat transferred between theone or more heat pipes and the heat exchanger is transferred via thethermal gap material, the thermal gap material having a thermalconductivity less than about 12 W/m-K.
 36. The system of claim 35,wherein a conduction length of the thermal gap and the thermalconductivity of the thermal gap material are arranged to define aworking temperature for the at least one heat pipe.
 37. The system ofclaim 36, wherein the thermal gap material includes liquid water and hasa thermal conductivity of about 0.6 W/m-K.
 38. The system of claim 35,further comprising a heat spreader between the at least one heat pipeand the thermal gap material and that is in direct thermal contact withthe at least one heat pipe and the thermal gap material.
 39. The systemof claim 38, wherein the heat spreader is metal and/or has thermalconductivity over 12 W/m-K.
 40. The system of claim 39, wherein the heatspreader includes a sleeve positioned over the heat pipe.
 41. The systemof claim 38, wherein the heat spreader has a cylindrical shape, apartial cylindrical shell configuration, is a sleeve and/or is a plate.42. The system of claim 35, wherein the heat receiving componentincludes a heat exchange fluid, one or more conduits to conduct a heatexchange fluid, a thermal storage device, a thermal storage medium,and/or one or more thermoelectric or other power conversion devices. 43.The system of claim 35, wherein the heat pipe includes a thermosiphon, aloop thermosiphon, a pulsating heat pipe, osmotic heat pipe and/or otherpossible specific configurations driven by other forces such aselectro-osmotic, acoustic, electrical, and/or magnetic.
 44. A method fordeploying a thermal coupling for a geothermal device, comprising:providing a heat exchanger in a geothermal well; providing one or moreheat pipes in the geothermal well, each of the heat pipes including acondenser section located nearer the heat exchanger than an evaporatorsection of the heat pipe; and providing a thermal gap material thatextends between, and thermally couples, the one or more heat pipes andthe heat exchanger such that more than 60% of heat transferred betweenthe one or more heat pipes and the heat exchanger is transferred via thethermal gap material, the thermal gap material having a thermalconductivity less than about 12 W/m-K.
 45. The method of claim 44,wherein a conduction length of the thermal gap and the thermalconductivity of the thermal gap material are arranged to define aworking temperature for the at least one heat pipe.
 46. The method ofclaim 44, wherein the thermal gap material includes liquid water and hasa thermal conductivity of about 0.6 W/m-K.
 47. The method of claim 44,further comprising providing a heat spreader between the at least oneheat pipe and the thermal gap material and that is in direct thermalcontact with the at least one heat pipe and the thermal gap material.48. The method of claim 47, wherein the heat spreader is metal and/orhas thermal conductivity over 12 W/m-K.
 49. The method of claim 48,wherein the heat spreader includes a sleeve positioned over the heatpipe.
 50. The method of claim 47, wherein the heat spreader has acylindrical shape, a partial cylindrical shell configuration, is asleeve and/or is a plate.
 51. The method of claim 44, further comprisingtransferring heat from the heat exchanger to a heat receiving componentthat includes a heat exchange fluid, one or more conduits to conduct aheat exchange fluid, a thermal storage device, a thermal storage medium,and/or one or more thermoelectric or other power conversion devices. 52.The method of claim 44, wherein the one or more heat pipes includes athermosiphon, a loop thermosiphon, a pulsating heat pipe, and/or anosmotic heat pipe.
 53. A heat pipe and mounting component apparatus foruse with a heat exchanger in harvesting geothermal heat, comprising: oneor more heat pipes each having two end portions and an elongated centralportion; an upper collar arranged and dimensioned to engage with an endportion of the one or more heat pipes and to position the end portionwithin a specified distance of a perimeter of the heat exchanger locatedinside of the collar to define a thermal gap between the one or moreheat pipes and the heat exchanger; and an anti-buckling portion separatefrom the upper collar and attached to the one or more heat pipes at alocation below and away from the upper collar, the anti-buckling portionbeing releasably attached to the one or more heat pipes to allowmovement of the one or more heat pipes relative to the anti-bucklingportion in a direction along a length of the one or more heat pipes. 54.The system of claim 53, wherein the anti-buckling portion is attached tothe one or more heat pipes by a frangible connection, such as ametallurgical joint or adhesive, that fixes the heat pipes relative tothe anti-buckling portion until a force applied to the one or more heatpipes exceeds a threshold value.
 55. The system of claim 54, wherein thefrangible connection fixes the anti-buckling portion relative to theheat pipes and the upper collar until a force moving the upper collartoward the anti-buckling portion exceeds the threshold value.
 56. Thesystem of claim 53, wherein the upper collar and the anti-bucklingportion are movable toward each other so as to contact each other. 57.The system of claim 56, further comprising a lower guide portion thatincludes one or more heat pipe guides arranged to guide the one or moreheat pipes in deployment in the geothermal well in directions away fromthe heat exchanger.
 58. The system of claim 57, wherein theanti-buckling portion is positioned between the upper collar and lowerguide portion, and the upper collar is movable toward the lower guideportion to deploy the one or more heat pipes in the well.
 59. The systemof claim 58, further comprising a lower collar engaged with the one ormore heat pipes at a location below the upper collar and above theanti-buckling portion.
 60. The system of claim 53, wherein the uppercollar and/or the anti-buckling portion include two parts that areengagable with each other so as to receive a drill string or a portionof the heat exchanger between the two parts.
 61. The system of claim 53,wherein the heat pipe includes a thermosiphon, a loop thermosiphon, apulsating heat pipe, and/or osmotic heat pipe.
 62. A method fordeploying one or more heat pipes in a geothermal well for use with aheat exchanger in harvesting geothermal heat, comprising: providing oneor more heat pipes each having a first portion engaged with an uppercollar and a second portion engaged with an anti-buckling portionseparate from the upper collar and attached to the one or more heatpipes at a location below the upper collar and above a distal end of theone or more heat pipes; inserting the distal end of the one or more heatpipes into a corresponding well bore; exerting a force on the one ormore heat pipes so as to disengage the one or more heat pipes from theanti-buckling portion and allow the one or more heat pipes to move in adirection along a length of the one or more heat pipes relative to theanti-buckling portion; and arranging the upper collar adjacent a heatexchanger in the geothermal well.
 63. The method of claim 62, whereinthe anti-buckling portion is releasably attached to the one or more heatpipes by a frangible connection.
 64. The method of claim 62, wherein thestep of arranging the upper collar includes positioning a portion of theone or more heat pipes within a specified distance of a perimeter of theheat exchanger to define a thermal gap between the one or more heatpipes and the heat exchanger.
 65. The method of claim 62, furthercomprising providing a lower guide portion that includes one or moreheat pipe guides arranged to guide the one or more heat pipes indeployment in the geothermal well in directions away from the heatexchanger; and using the lower guide to guide movement of the one ormore heat pipes into respective bores during the inserting step.